Origin and Habitat: Frailea pumila occurs in Argentina (Entre Rios), Brazil (Rio Grande do Sul), Paraguay (Paraguarí) and Uruguay (Salto, Tacuarembó, Rivera and Artigas) The species is abundant where it occurs, but its distribution is sparse.Altitude: 20 to 300 meters above sea level.Habitat: They grow in Pampa grasslands on rocky outcrops, stony fields, rocky beds of creeks or in areas of flat rock outcrops subjected to seasonal flooding. The plants are most plentiful in the places which are flooded during the episodes of intense rain. In these places F. pumila grows in the crevices of the rocks together with mosses and lichens, the plants firmly attached to the rocks by their strong tuberous roots. For most of their life they stay pretty much hidden in the grass, but every now and then they come forth with a halo of bright yellow flowers, attracting any pollinators in the vicinity. The same areas support endemic succulents and xerophyte plants such as Frailea asterioides, Frailea phaeodisca and Frailea schilinzkyana (Frailea perumbilicata) and Notocactus mammulosus. The major threats in are grazing and cattle trampling, agriculture, forestry of Eucalyptus, invasive grasses and fire.

Description:Frailea pumila is one of the largest of the globular species, attaining a diameter of up to five centimetres. It has many low, tuberculate ribs, while the areoles have whitish felt and about 18 radial spines that are more or less curved and point in all directions.Habit: Plant cespitose, sprouting around the base to form clumps.Roots: It has a well-developed contractile tuberous root system. These tuberose roots have the function of storing enough sustenance so that plants can survive the periods of drought that they have to endure. Tuberous roots also have the function of anchoring the plants into the ground. Stem: Sub-globular, flattened and umbilicate at apex, 2-5 cm in diameter and 2 cm high, deep green, sometimes becoming reddish.Ribs: 13 to 20, flat, more distinct than in the related species, more or less tuberculate.Areoles: Small, nearly circular.Spines: All pubescent, 1-5 mm long, yellowish brown not readily distinguishable as centrals and radialsRadial spines: 9 to 14, setaceous, more or less appressed.Central spines: 1-2(-3), erect.Flower: 2 cm long, yellow; axils of scales on the ovary and flower-tube woolly and setose. Fruits: Green.Seeds: Smooth, brown, obovate, 1,5 mm long, angled on the back; depressed hilum much smaller than in Frailea cataphracta.

Subspecies, varieties, forms and cultivars of plants belonging to the Frailea pumila group

Frailea camaquensisL.Horst: becomes more cylindrical with time. Distribution: West of Minas de Camaqua, Rio Grande do Sul, Brazil

Notes: Fraileas are cleistogamous meaning that their flowers produce seed without even opening. Without the need for pollination, hence the buds rarely reach full bloom and remain closed. They usually produce little round, dry fruits without flowering. It would be a mistake to believe that this is always the case: Frailea pumila, is able to produce flowers which open normally.The accepted opinion is that Frailea flowers only open in full sun, otherwise fruits will form cleistogamously. In reality relations are quite different: Both Frailea grahliana and Frailea schilinskyana produce buds in the form of a miniature plant of barely 10 mm in section, which do not open but which may still become seed-bearing fruits. Only when the young plants grow larger and are amply surrounded with offsets, do buds develop which pass into open flowers. Plants having open flowers for the first time, also produce again in the following year (pre-supposing that growth continues in the same manner) a few cleistogamous flowers first and after that open flowers. Only when the plants are so large that they flower with open flowers right at the start of the season, does this ability apply to even the smallest offset. Frailea aurea, Frailea carminifilamentosa, Frailea pseudograhliana, and Frailea pumilia, behave in this same way. Larger-growing Fraileas such as Frailea bruchii, Frailea dadakii, Frailea pygmaea, which seldom make offsets, bear fewer flowers. Here again, open flowers only appear on older plants. For every standstill in growth, the plant answers with cleistogamous flowers - in the summer weather too. In the event of the standstill in growth occurring in spring - for instance owing to repotting - then open flowers only come in summer. This will have led to the wrong opinion, that Fraileas flowers only open in full sunshine. Cleistogamous buds are initially conical, then shortly a change occurs in the bud development - that part of the bud at the base starts growing thicker and petals are never formed. The buds that form flowers grow a slender egg shape and open quite some time later. Under normal circumstances the flowers opens in the greenhouse at a temperature above 20°C. They stay open only a few hours around noon, and they do not open again the next day. It is of interest that most of the open flowers do not form seeds if, one does not assist by pollinating by hand. [W. Simon “The behaviour of some cacti during fertilisation cleistogamy.” The Chileans '69 pp.18-20 Volume 3 Number 14 (Translated from Succulenta for May 1967 by H. Vriend) <http://www.grahamcharles.org.uk/Chileans%20editions/Issue14.pdf>]

Cultivation and Propagation: Frailea pumila is a summer grower species relatively easy to grow. It is sometime seen as a grafted plant but grows very well on its own roots too. Characteristically, during the dry season plants retract completely under the ground both in the wild and in cultivation too.Growth rate: Fraileas are relatively short-lived plants, only lasting few years (rarely more than 10-15 years in cultivation) and, possible annuals in habitat! In fact they reseed readily around the base of the mother plant from self-set seed if kept reasonably moist during warm weather. It is agood idea to keep restarting them from seed; what looks like a healthy big plant may suddenly die of old age without warning.Soil: Use mineral well permeable substratum with little organic matter (peat, humus), plants may become too elongated if compost is too rich.Repotting: Re-pot every 2 years. Use pot with good drainage.Fertilization: It grows much faster with a low nitrogen content fertilizer in spring and summer. Potassium helps maintaining the plants compact and healthy. Watering: Requires careful watering to keep plant compact. Water sparingly from March till October, the thin, fibrous roots suffer if there is humidity, therefore the plant should be watered only when the surrounding terrain is dry. Keep dry as soon as the temperature starts dropping in October and keep it perfectly dry in winter at temperatures from 5 to 15 degrees centigrade.Hardiness: They need a minimum temperature of 5-10° C (but occasionally temperatures of a few degrees below 0° are not dangerous if kept on the dry side prior to, and during, cold weather). It tends to rot in winter during the resting phase, if kept wet. In the rest period no high atmospheric humidity!!Sun Exposure: Light shade to full sun, its colour tends to richer and darker when grown in light shade. In a shaded position the plants grow faster, but are not flat shaped and dark coloured.Uses: It is an excellent plant for container growing. It always looks good and stays small. Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for: - Red spiders: Red spiders may be effectively rubbed up by watering the infested plants from above.- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects. - Scales: Scales are rarely a problem. - Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much. To prevent rottenness it is also advisable to surround its root neck by very rough sand or grit, this help a fast water drainage.Propagation: With fresh harvested seeds or (rarely) by grafting. Fraileas set seed (when well grown) and grow easily from seed. In fact, they are reported to set seed even if the flower doesn’t open. This self-fertilization is called cleistogamy. Seedlings dislike strong light and dry conditions and need to be repotted frequently during the first few years. However, old plants become senile and have a tendency to succumb to disease and a weak root system. At this stage, as is well known, they die suddenly. So, after they reach about 4-5 cm in diameter grow them slowly, and adopt a new repotting period, using intervals of every 3-4 years. Additionally grow them under drier conditions or with stronger sunlight. But plants are sometine grafted to accelerate growth, but the grafted plants are typical rather tall growing, compared with plants on their own roots that are usually more flat to the ground.